DESCRIPTION

Only limited information has previously been compiled on the long-term performance of large-scale decentralized or community-sized wastewater collection and treatment/disposal systems for use by practitioners, planners, regulators, and decision makers. Factors contributing to the shortage of information vary by region and regulatory jurisdiction. Due to their age and condition, many of these systems may soon require upgrading or replacement to meet current requirements. Adding to the need to compile good quality performance data for large-scale decentralized systems is the perception that property developers frequently arrange for wastewater service that results in the least short-term investment rather than the lowest life-cycle costs. Such choices are likely based largely on the absence of readily available information that could help with that decision-making process. By contrast, centralized systems are often at least partially planned, funded, and managed by utilities that are ultimately accountable to rate-payers who provide an accompanying driver to minimize life-cycle costs. Far more operations and performance data has been compiled and made available to the public for larger centralized systems.

This nationwide study has gathered data/information for and examined the performance of large-scale decentralized and small community wastewater systems with flows ranging from 5,000 to 50,000 gallons per day with at least five years of operating history. The study covers systems handling domestic waste flows only (residential and commercial facilities) that have been designed and constructed in accordance with regulatory requirements and accepted industry practices applicable to the particular state or region. Systems relying either on soil/land disposition or direct discharge of effluent were included in those studied. The results of the project will better enable designers, regulators, and the industry as a whole to better assess and select decentralized systems used to serve certain types of facilities in various geographic settings. A companion Research Digest summarizes the key findings that are in the final report.